[petsc-dev] PETSc-Cuda with gfortran 4.7

[Nystrom, William D]

Hi Karli,

I'm not sure what point you are trying to make below.  As I indicated in my emails, I am using
4.7.2 compilers for everything except nvcc and 4.7.2 is the default version of compilers for my
distro, Fedora 17.  However, nvcc constrains the version of compilers based on the Cuda
distribution.  Cuda 5.0 requires 4.6.x or earlier.  Cuda 4.2 requires 4.5.x or earlier, etc.  Perhaps
Cuda 5.1 will support 4.7.x but I have no idea when it will be released.  The procedure I shared
below allows one to restrict use of 4.6.x to only nvcc.

Also, I don't have experience with other distros like Debian or Ubuntu.  So I can't speak with any
confidence on them although I don't see why the nvcc.profile approach would depend on the
distro.

Also, I'm just trying to share my experiences with building petsc in a 4.7.2 compiler environment
to help Asmund.  If this is not appropriate for this mailing list, I'm happy to communicate directly
with Asmund.

Best regards,

Dave

________________________________________
From: petsc-dev-bounces at mcs.anl.gov [petsc-dev-bounces at mcs.anl.gov] on behalf of Karl Rupp [rupp at mcs.anl.gov]
Sent: Friday, March 15, 2013 9:43 AM
To: For users of the development version of PETSc
Cc: Åsmund Ervik
Subject: Re: [petsc-dev] PETSc-Cuda with gfortran 4.7

Hi guys,

depending on the distribution you are using, there may be multiple
versions of GCC already in the repository. For example, on Debian-based
distributions you can have multiple versions of GCC installed, which
show up in the package manager as gcc-4.6, gcc-4.7, etc.

Ubuntu for example even allows you to switch between the versions
seamlessly using
  $> sudo update-alternatives --config gcc
An example can be found here:
http://askubuntu.com/questions/182027/how-to-use-gcc-4-7-in-place-of-4-6-ubuntu-12-04

Aside from that, it is still not satisfactory for us to keep
recommending other compilers. GCC 4.7 will soon be the default on many
distributions (if it isn't already)...

Best regards,
Karli



On 03/15/2013 10:36 AM, Nystrom, William D wrote:
> Hi Asmund,
>
> In petsc-dev, files with a .cu extension are compiled with nvcc.
>
> I also tried the suggestion of soft linking an acceptable version of gcc/g++ into
> /usr/local/cuda/bin.  I think I used a gcc/g++ from a compatibility package that
> I installed with yum.  That did not work for me either.  I think the issue might
> have been related to that version being in the ccache directory but am not sure.
> The only solution I got to work was to install a new, acceptable version of the
> GNU compilers by actually building from source and installing in its own location
> such as somewhere in your home directory or in some place like /usr/local or
> /opt.  Also, if you use the "--program-suffix=46" configure option, I think you
> may also need to softlink gcc46 to gcc and g++46 to g++ in your install directory.
> I could check that when I get home this evening as well as checking my build
> script to make sure there is not something important in it to pass on.
>
> For me, it took about about an hour to build gcc 4.6.3, once I had learned the
> various things I passed on in the earlier email.  So you may have to just build
> a version of gcc rather than using a version from your distro's package system.
> BTW, what distro are you using?  I don't believe that nvcc uses gfortran.  It uses
> g++ and maybe also gcc.  Also, there is nothing special about gcc 4.6.3.  You
> could build an earlier version of gcc such as gcc 4.5.x or gcc 4.4.x.  I chose
> gcc 4.6.3 because it was the most up to date version that was supported by
> nvcc from the Cuda 5 distribution.
>
> I'll write more from home this evening when I can check some things on my
> system.
>
> Cheers,
>
> Dave
>
> ________________________________________
> From: Åsmund Ervik [Asmund.Ervik at sintef.no]
> Sent: Friday, March 15, 2013 7:21 AM
> To: petsc-dev at mcs.anl.gov; Nystrom, William D
> Subject: Re: [petsc-dev] PETSc-Cuda with gfortran 4.7
>
> Hi Dave,
>
> The errors occur when compiling these CUDA files:
> mpiaijAssemble.cu, aijcusp.cu, mpicusp.cu and veccusp.cu
> I assume these are compiled with nvcc, but I haven't triple checked that.
>
> I had not tried your trick with setting the C compiler in nvcc.profile.
> I did, however, try symlinking gcc-4.4 binaries into /usr/local/cuda/bin
> (as was suggested in one stackexchange post I found), but this produced
> an error during configure. Using your nvcc.profile, it gives the same error:
>
> CUDA version error: PETSC currently requires CUDA version 4.0 or higher
> - when compiling with CUDA
>
> Even though I have CUDA 5.0 installed. Just to be sure, are there
> binaries beside gfortran, gcc and g++ which must be found in the
> CUDA-specific gcc-4.6 folder? I have both gcc variants installed through
> the packaging system of my distro, so I cant't tell which belong to the
> 4.6 variant.
>
> Asmund
>
> On 13. mars 2013, wdn at lanl.gov wrote:
>>
>> Asmund,
>>
>> Do the failures you report below occur in cuda code that is ultimately compiled with nvcc?
>> I have not had problems compiling petsc-dev with cuda support on a Fedora 17 system
>> which uses gcc-4.7.2 and gfortran-4.7.2.  However, I have gcc 4.6.3 installed also and
>> have nvcc pointed at it by using the /usr/local/cuda/bin/nvcc.profile with a couple of lines
>> added.  So, when I build petsc-dev on my Fedora 17 system, it uses gcc-4.7.2 and
>> gfortran-4.7.2 for everything except cuda code located in .cu files.  I would worry about
>> removing some functionality in 4.7.2 with your suggested modification.
>>
>> Thanks,
>>
>> Dave
>>
>> --
>> Dave Nystrom
>> LANL HPC-5
>> Phone: 505-667-7913
>> Email: wdn at lanl.gov
>> Smail: Mail Stop B272
>>         Group HPC-5
>>         Los Alamos National Laboratory
>>         Los Alamos, NM 87545
>>
>>